PEER REVIEW
20
th
Australian International Aerospace Congress, 27-28 November 2023, Melbourne
ISBN number: 978-1-925627-66-4
Change Detection for Improved Maintenance Notification
and Remaining Useful Life Calculation
Eric Bechhoefer
1
, and Christian Janke
2
GPMS International Inc, 93 Pilgrim Park Rd, Waterbury, VT, 05676, USA
2
Embry-Riddle, College of Aeronautics,
1 Aerospace Boulevard, Daytona Beach, FL 32114, USA
Abstract
HUMS (Health and Usage Monitoring Systems) provide enhanced safety and availability by
alerting maintenance personnel when components (shaft/gears/bearings) have degraded or
become damaged. Proactive maintenance ensures that a degraded component will not fail in
flight. Often, the damage is from high cycle fatigue or other relatively slow degradation
processes. However, there are events, such as maintenance, that result in a step-change in the
component's health. While high cycle fatigue degradation can be trended, a step-change in
component health presents a challenge.
For example, HUMS data from recent maintenance on a Thompson coupling resulted in a large
3/rev increase in vibration, which caused a step-change in the coupling health. Trending tools,
which are, in effect, low-pass filters, would not immediately alert maintenance or the crew to
the anomaly. Thus, a process to detect the change in health is needed which is both sensitive to
change and provides protection against false alarms.
Change detection in manufacturing process control has long been used for quality control.
Several statistical tools have been developed to alert when the manufacturing status is out of
specification. However, the research team is interested in determining when the high-cycle
fatigue process is out of control. That is, when the difference between the component health
trend, and measured component health, are statistically different enough, an alert should be sent
to the maintainer, and the trend is reset to reflect the step-change.
This paper describes the development of a CUSUM (cumulative sum) statistic between a
component health trend and the measured component health. This allows the automated capture
of maintenance or other events that would result in a component step-change in health.
Keywords: CUSUM, Health indicator, Maintenance alert, RUL, Smith Chart.
Introduction
Health and Usage Monitoring Systems (HUMS) were able to provide the most benefits and
safety gain in rotorcraft aviation. HUMS supports several functions that improve safety by
proactively reporting the performance of the aircraft. Those functions may include notification
of flight manual exceedance, flight data monitoring to support a safety management system,
automated engine performance checks, drivetrain diagnostics, or rotor track and balance.
Collectively, HUMS provides actionable information so that maintainers can make data-
informed decisions (Ref 1).
